Thus far, a square battery has been known as a battery that can provide a larger volume density than a cylindrical battery. A square battery accommodates a flat wound electrode group formed by stacking a band-like positive electrode and a band-like negative electrode through a separator and winding them in a square battery chassis, and an electrolytic solution is injected into the battery chassis.
The square battery has respective uncoated portions of the positive electrode and the negative electrode protruding at both end portions of the flat wound electrode group in the winding axis direction, and allows an electrode terminal or a collector to be connected to the uncoated portions, thereby minimizing the conducting path so as to reduce connection resistance and increase the output. In addition, the above configuration is effective for making the battery compact.
Regarding the connection aspect between the flat wound electrode group and the collector, for example, a storage element of PTL 1 has been proposed.
In the storage element described in PTL 1, plate-like sheet connection portions are inserted inward from the end surfaces of the uncoated portions protruding from the flat wound electrode group so as to connect both portions.